Display device

ABSTRACT

According to an aspect, a display device includes: a substrate having a display region;
         a shield conductive layer provided above the substrate; and a plurality of wiring units for temperature detection disposed at positions overlapping with the display region and the shield conductive layer when seen in a plan view. Each wiring unit for temperature detection has one end coupled to a first wire and the other end coupled to a second wire to detect resistance that changes in accordance with a change in temperature, between the first wire and the second wire.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/773,470, filed on Jan. 27, 2020, which application claims priorityfrom Japanese Application No. 2019-013622, filed on Jan. 29, 2019, thecontents of which are incorporated by reference herein in its entirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a display device.

2. Description of the Related Art

A display device that projects images on a translucent member, such asglass, is known as a so-called head-up display (HUD), which is disclosedin Japanese Patent Application Laid-open Publication No. 2015-210328(JP-A-2015-210328), for example.

According to the technology of JP-A-2015-210328, the display device mayintroduce sunlight through an optical system. If sunlight collected bythe optical system strikes the display device, the display device maydeteriorate.

Japanese Patent Application Laid-open Publication No. 2016-051090(JP-A-2016-051090) discloses a liquid crystal display device including atemperature sensor disposed outside a display region. Since the incidentstate of sunlight changes with a relative position between the sun andthe display device, the temperature sensor described inJP-A-2016-051090, which is disposed outside the display region, may failto detect the sunlight collected by the optical system.

For the foregoing reasons, there is a need for a display device that candetect a partially heated state of a display region.

SUMMARY

According to an aspect, a display device includes: a substrate having adisplay region; a shield conductive layer provided above the substrate;and a plurality of wiring units for temperature detection disposed atpositions overlapping with the display region and the shield conductivelayer when seen in a plan view. Each wiring unit for temperaturedetection has one end coupled to a first wire and the other end coupledto a second wire to detect resistance that changes in accordance with achange in temperature, between the first wire and the second wire.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram for schematically explaining a head-up display;

FIG. 2 is a diagram for schematically explaining a display device;

FIG. 3 is a diagram for explaining pixels of the display device;

FIG. 4 is a schematic sectional view of the display device;

FIG. 5 is a plan view for explaining the arrangement of wiring units fortemperature detection;

FIG. 6 is an enlarged plan view of a region Ra illustrated in FIG. 5;

FIG. 7 is a process chart for explaining a manufacturing method of thewiring units for temperature detection according to a first embodimentof the present disclosure;

FIG. 8 is a graph illustrating a resistance change rate of one wiringunit for temperature detection with respect to a temperature;

FIG. 9 is a graph for explaining an exemplary distribution of resistancechange rates of the wiring units for temperature detection;

FIG. 10 is a sectional view for explaining a wiring unit for temperaturedetection according to a second embodiment of the present disclosure;and

FIG. 11 is a sectional view for explaining a wiring unit for temperaturedetection according to a third embodiment of the present disclosure.

DETAILED DESCRIPTION

Exemplary aspects (embodiments) to embody the present disclosure aredescribed below in greater detail with reference to the accompanyingdrawings. The contents described in the embodiments are not intended tolimit the present disclosure. Components described below includecomponents easily conceivable by those skilled in the art and componentssubstantially identical therewith. Furthermore, the components describedbelow may be appropriately combined. What is disclosed herein is givenby way of example only, and appropriate changes made without departingfrom the spirit of the present disclosure and easily conceivable bythose skilled in the art naturally fall within the scope of thedisclosure. To simplify the explanation, the drawings may possiblyillustrate the width, the thickness, the shape, and other elements ofeach unit more schematically than the actual aspect. These elements,however, are given by way of example only and are not intended to limitinterpretation of the present disclosure. In the present disclosure andthe figures, components similar to those previously described withreference to previous figures are denoted by like reference signs, anddetailed explanation thereof may be appropriately omitted. In thisdisclosure, when an element A is described as being “on” another elementB, the element A can be directly on the other element B, or there can beone or more elements between the element A and the other element B.

First Embodiment

FIG. 1 is a diagram for schematically explaining a head-up display. Ahead-up display (hereinafter referred to as HUD) device 1 includes abacklight 6, a diffuser 9, a display device 2, a windshield WS, and anoptical system RM that enlarges and projects an image from the displaydevice 2 onto the windshield WS.

A housing 4 houses the backlight 6 serving as a light source device, thedisplay device 2 that outputs an image using light L from the backlight6 as the light source, the diffuser 9 provided between the displaydevice 2 and the backlight 6, and the optical system RM. The light Lemitted from the backlight 6 is diffused by the diffuser 9, andpartially or entirely transmitted through the display device 2. Thelight L is then reflected by the optical system RM and the windshield WSand reaches a user H. The user H recognizes the light L as an image VIwithin the field of view of the user H. In other words, the displaydevice 2 according to a first embodiment functions as the HUD device 1including the optical system RM and the windshield WS. The windshield WSmay be any translucent member disposed on the line of sight of the userH, and may be, for example, glass of a front windshield of a vehicle.

The optical system RM of the HUD device 1 according to the firstembodiment includes a mirror RM1 and a mirror RM2 that guide the light Ltransmitted through the display device 2. The mirror RM1 is a planemirror and the mirror RM2 is a concave mirror. The mirror RM1 may alsobe a concave mirror. The optical system RM is not limited to thisstructure, and may be configured by a single mirror or three or moremirrors.

The following describes the display device 2. FIG. 2 is a diagram forschematically explaining the display device. FIG. 3 is a diagram forexplaining pixels of the display device. FIG. 4 is a schematic sectionalview of the display device. FIG. 5 is a plan view for explaining thearrangement of wiring units for temperature detection. The displaydevice 2 according to the first embodiment is a transmissive liquidcrystal display that outputs an image by using the light L emitted fromthe light source. The display device 2 includes a display driverintegrated circuit (DDIC) 19.

The display device 2 is also called as a display panel. As illustratedin FIG. 2, the display device 2 has a display region AA, in which aplurality of pixels VPix are arranged in a matrix (row-columnconfiguration).

As illustrated in FIG. 3, each pixel VPix includes a plurality ofsub-pixels SPix. Each sub-pixel SPix includes a switching element Tr anda liquid crystal capacitor 8 a. The switching element Tr is a thin filmtransistor (TFT). In this example, the switching element Tr is ann-channel metal oxide semiconductor (MOS) TFT. An insulating layer 24 isprovided between a pixel electrode 22 and a common electrode COM, and aholding capacitor 8 b illustrated in FIG. 3 is formed by these elements.

As illustrated in FIG. 2, a control circuit 110 functions as, forexample, a display control circuit 111 and a light-source controlcircuit 112. The display control circuit 111 outputs, to the DDIC 19,signals such as a master clock signal, a horizontal synchronizingsignal, a vertical synchronizing signal, a pixel signal, and a drivecommand signal for driving the backlight 6. The pixel signal is a signalcombining gradation values of, for example, red (R), green (G), and blue(B). The display control circuit 111 controls the output gradationvalues of part or all of the pixels in accordance with the amount oflight emitted from light sources 61 controlled by the light-sourcecontrol circuit 112. The light-source control circuit 112 controls theoperation of the light sources 61 in synchronization with the pixelsignals.

The switching elements Tr of the respective sub-pixels SPix illustratedin FIG. 3, signal lines SGL, and gate lines GCL, for example, are formedon a first substrate 21 (see FIG. 4). The signal lines SGL are wiringfor supplying the pixel signals to pixel electrodes 22 illustrated inFIG. 4. The gate lines GCL are wiring for supplying drive signals to theswitching elements Tr. The signal lines SGL and the gate lines GCLextend along a plane parallel to the surface of the first substrate 21.

The DDIC 19 illustrated in FIG. 2 sequentially selects the gate linesGCL as a gate driver. The DDIC 19 applies a scan signal to the gate ofthe switching element Tr in the sub-pixel SPix through the selected gateline GCL. In this manner, the sub-pixels SPix are sequentially selectedrow by row (by each horizontal line).

The DDIC 19 supplies the pixel signals to the sub-pixels SPix includedin the selected horizontal line through the signal lines SGL as a sourcedriver. The sub-pixels SPix display an image on a horizontalline-by-horizontal line basis in accordance with the provided pixelsignal.

The DDIC 19 applies a common potential to the common electrode COM as acommon electrode driver. The common potential is a direct-currentvoltage signal applied in common to the sub-pixels SPix.

As described above, the DDIC 19 functions as the gate driver, the sourcedriver, and the common electrode driver. The DDIC 19 may have separateconfigurations of the gate driver, the source driver, and the commonelectrode driver. Alternatively, at least one of the gate driver, thesource driver, and the common electrode driver may be formed on thefirst substrate 21 by using the TFTs.

A color filter 32 illustrated in FIG. 3 may have color regions coloredin, for example, red (R), green (G), and blue (B) that are periodicallyarranged. Color regions 32R, 32G, and 32B having the colors of R, G, andB, respectively, correspond to the respective sub-pixels SPixillustrated in FIG. 3 and serve as a set. A set of sub-pixels SPixcorresponding to the respective color regions 32R, 32G, and 32B of thethree colors constitutes a pixel VPix. The color filter 32 may includecolor regions of four or more colors.

As illustrated in FIG. 2, a plurality of wiring units for temperaturedetection SM are arrayed. Both terminals of the wiring unit fortemperature detection SM are pulled out and electrically coupled to aresistance detection circuit 120. The resistance detection circuit 120converts a resistance value of the wiring unit for temperature detectionSM from analog to digital and outputs the detected resistance signal tothe control circuit 110.

The following describes an exemplary configuration of the display device2 according to the first embodiment. FIG. 4 is a schematic sectionalview of the display device. As illustrated in FIG. 4, the display device2 includes a pixel substrate 20, a counter substrate 30, and a liquidcrystal layer 8 serving as a display function layer. The countersubstrate 30 faces the pixel substrate 20 in a direction perpendicularto the surface of the pixel substrate 20. The liquid crystal layer 8 isprovided between the pixel substrate 20 and the counter substrate 30.

The pixel substrate 20 includes the first substrate 21, the pixelelectrodes 22, the common electrode COM, and a polarizing plate 65. Thefirst substrate 21 is provided with the switching elements Tr such asthe TFTs and various wiring such as the gate lines GCL and the signallines SGL, which are not illustrated in FIG. 4.

The common electrode COM is provided on the upper side of the firstsubstrate 21. The pixel electrodes 22 are provided on the upper side ofthe common electrode COM with the insulating layer 24 interposedtherebetween. The pixel electrodes 22 are provided in a layer differentfrom that of the common electrode COM and overlap with the commonelectrode COM in a plan view. The pixel electrodes 22 are arranged in amatrix (row-column configuration) in a plan view. The polarizing plate65 is provided on the lower side of the first substrate 21 with anadhesive layer 66 interposed therebetween. The pixel electrodes 22 andthe common electrode COM are made of a translucent conductive material,such as indium tin oxide (ITO). While the present embodiment has beendescribed with reference to the example in which the pixel electrodes 22are provided on the upper side of the common electrode COM, the commonelectrode COM may be provided on the upper side of the pixel electrodes22.

The first substrate 21 is provided with the DDIC 19 and a flexiblesubstrate 71. The DDIC 19 functions as the control circuit 110illustrated in FIG. 2.

In the first embodiment, the direction perpendicular to the surface ofthe first substrate 21 and extending from the first substrate 21 towarda second substrate 31 is defined as the “upper side”. The directionextending from the second substrate 31 toward the first substrate 21 isdefined as the “lower side”.

The counter substrate 30 includes: the second substrate 31; the colorfilter 32 formed on one surface of the second substrate 31; a shieldconductive layer 51 provided on the other surface of the secondsubstrate 31; the wiring units for temperature detection SM; aprotection layer 38; an adhesive layer 39; and a polarizing plate 35.The wiring units for temperature detection SM are arrayed on the secondsubstrate 31. The second substrate 31 is coupled to a flexible substrate72. The wiring units for temperature detection SM are electricallycoupled to the flexible substrate 72 through terminals 36. The flexiblesubstrate 72 is coupled to the resistance detection circuit 120illustrated in FIG. 2. The detailed configuration of the wiring unitsfor temperature detection SM will be described later. The shieldconductive layer 51 is interposed between the second substrate 31 andthe wiring units for temperature detection SM in a directionperpendicular to the surface of the second substrate 31.

The wiring units for temperature detection SM include first conductivethin wires 33U and second conductive thin wires 33V. The protectionlayer 38 is provided on the wiring units for temperature detection SM toprotect the wiring units for temperature detection SM including thefirst conductive thin wires 33U and the second conductive thin wires33V. The protection layer 38 can be made of a translucent resin, such asan acrylic resin. The polarizing plate 35 is provided above theprotection layer 38 with the adhesive layer 39 interposed therebetween.The adhesive layer 39 is an insulating layer having a higher resistancevalue than that of the wiring units for temperature detection SM.

The shield conductive layer 51 is a translucent conductive layer and ismade of, for example, ITO, indium zinc oxide (IZO), tin oxide (SnO), oran organic conductive film. The shield conductive layer 51 may employ,for example, an oxide layer composed mostly of tin oxide (SnO₂) andsilicon dioxide (SiO₂), an oxide layer composed mostly of gallium oxide(Ga₂O₃), indium oxide (In₂O₃), and tin oxide (SnO₂), or a translucentconductive layer composed mostly of ITO and including silicon (Si).

The first substrate 21 and the second substrate 31 are spaced apart at acertain distance. The space between the first substrate 21 and thesecond substrate 31 is sealed with a sealing member 69. The liquidcrystal layer 8 is provided in a space surrounded by the first substrate21, the second substrate 31, and the sealing member 69. The liquidcrystal layer 8 modulates light passing therethrough in accordance withthe state of an electric field, and employs liquid crystals in atransverse electric field mode such as an in-plane switching (IPS) modeincluding a fringe field switching (FFS) mode. An orientation film,which is not illustrated, is provided between the liquid crystal layer 8and the pixel substrate 20 and between the liquid crystal layer 8 andthe counter substrate 30 illustrated in FIG. 4. In the first embodiment,the liquid crystal layer 8 is driven by a transverse electric filedgenerated between the pixel electrodes 22 and the common electrode COM.

The backlight 6 illustrated in FIGS. 1 and 2 is provided at the lowerside of the first substrate 21. Light emitted from the backlight 6passes through the pixel substrate 20, and is modulated in accordancewith the state of liquid crystals at respective positions. The state oflight transmittance toward the display surface changes depending on thepositions. In this manner, the display device 2 displays an image on thedisplay region AA.

FIG. 5 is a plan view for explaining the arrangement of the wiring unitsfor temperature detection. FIG. 4 is a sectional view taken along lineIV-IV in FIG. 5. As illustrated in FIG. 5, the wiring units fortemperature detection SM according to the first embodiment each includea plurality of first conductive thin wires 33U and a plurality of secondconductive thin wires 33V. The first conductive thin wires 33U and thesecond conductive thin wires 33V are inclined in mutually oppositedirections with respect to the direction parallel to one side of thedisplay region AA. The first conductive thin wires 33U form a firstangle with a first direction Dx and the second conductive thin wires 33Vform a second angle with the first direction Dx. When the firstconductive thin wires 33U and the second conductive thin wires 33V neednot be distinguished from each other, they are collectively referred toas conductive thin wires 33 herein below.

Each of the first conductive thin wires 33U and the second conductivethin wires 33V is a metallic wire having a narrow width. In the displayregion AA, the first conductive thin wires 33U are spaced apart fromeach other in a direction crossing the extending direction of the firstconductive thin wires 33U, i.e., in a second direction Dy. The secondconductive thin wires 33V are spaced apart from each other in the seconddirection Dy.

Each wiring unit for temperature detection SM includes at least onefirst conductive thin wire 33U and at least one second conductive thinwire 33V crossing the first conductive thin wire 33U. The firstconductive thin wire 33U and the second conductive thin wire 33V areelectrically coupled at a node 33X. When the first conductive thin wires33U cross the second conductive thin wires 33V, the shape of a meshformed in the wiring unit for temperature detection SM is aparallelogram.

One ends in the extending direction of the first conductive thin wires33U and the second conductive thin wires 33V are coupled to a couplingwire 34 a, and the other ends in the extending direction of the firstconductive thin wires 33U and the second conductive thin wires 33V arecoupled to a coupling wire 34 b, the coupling wire 34 a and the couplingwire 34 b being disposed in a peripheral region FR. The first conductivethin wires 33U and the second conductive thin wires 33V, which are maindetectors of the wiring unit for temperature detection SM, are coupledto the coupling wires 34 a and 34 b through third conductive thin wires33 a. The first conductive thin wires 33U and the second conductive thinwires 33V are electrically coupled to each other to function as onewiring unit for temperature detection SM.

The first conductive thin wires 33U and the second conductive thin wires33V are made of a metal layer including one or more metals selected fromaluminum (Al), copper (Cu), silver (Ag), molybdenum (Mo), chromium (Cr),titanium (Ti), and tungsten (W). Alternatively, the first conductivethin wires 33U and the second conductive thin wires 33V are made of analloy layer including one or more metals selected from aluminum (Al),copper (Cu), silver (Ag), molybdenum (Mo), chromium (Cr), titanium (Ti),and tungsten (W). The first conductive thin wires 33U and the secondconductive thin wires 33V can be made of an aluminum alloy such as AlNd,AlCu, AlSi, and AlSiCu. The first conductive thin wires 33U and thesecond conductive thin wires 33V may be a multilayered body ofconductive layers made of these metals or a multilayered body of alloyconductive layers including one or more of these metals.

A width of each of the first conductive thin wire 33U and the secondconductive thin wire 33V is preferably from 1 μm to 10 μm inclusive, andmore preferably, from 1 μm to 5 μm inclusive. This is because settingthe width of the first conductive thin wire 33U and the secondconductive thin wire 33V to 10 μm or smaller can reduce the areacovering an aperture that is a region where light transmittance is notsuppressed by the gate lines GCL and the signal lines SGL in the displayregion AA, thereby reducing the probability of a loss of the apertureratio. This is also because setting the width of the first conductivethin wire 33U and the second conductive thin wire 33V to 1 μm or largerstabilizes the shape of the wires, thereby lowering the probability ofdisconnection.

Each wiring unit for temperature detection SM includes the firstconductive thin wires 33U and the second conductive thin wires 33V thatare arranged at a predetermined pitch, and extends, as a whole, in adirection crossing the extending direction of the color regions 32R,32G, and 32B of the color filter 32. In other words, the wiring unit fortemperature detection SM extends in the first direction Dx crossing thesignal lines SGL illustrated in FIG. 3. In order for the firstconductive thin wires 33U and the second conductive thin wires 33V notto block light from reaching a specific color region of the color filter32, the first conductive thin wires 33U and the second conductive thinwires 33V form a mesh shape such that thin wire pieces inclined inmutually opposite directions cross each other and are coupled to eachother. The first conductive thin wires 33U and the second conductivethin wires 33V are inclined in the mutually opposite directions at anangle θ with respect to a direction parallel to the extending direction(second direction Dy) of the color regions 32R, 32G, and 32B. The angleθ is, for example, from 5 degrees to 75 degrees inclusive. Morepreferably, the angle θ is from 25 degrees to 40 degrees inclusive, andstill more preferably, from 50 degrees to 65 degrees inclusive.

In this manner, the extending directions of the first conductive thinwires 33U and the second conductive thin wires 33V of the wiring unitfor temperature detection SM have a certain angle with respect to theextending direction of the color regions 32R, 32G, and 32B of the colorfilter 32. As a result, the first conductive thin wires 33U and thesecond conductive thin wires 33V of the wiring unit for temperaturedetection SM sequentially block light from reaching the color regions32R, 32G, and 32B of the color filter 32. This configuration can preventlower transmittance in a specific color region of the color filter 32.The arrangement of the first conductive thin wires 33U and the secondconductive thin wires 33V of the wiring unit for temperature detectionSM may be varied within an acceptable range. In other words, the firstconductive thin wires 33U and the second conductive thin wires 33V ofthe wiring unit for temperature detection SM may be arranged atdifferent intervals.

FIG. 6 is an enlarged plan view of a region Ra illustrated in FIG. 5. Asillustrated in FIG. 6, the wiring unit for temperature detection SMincludes sensor portions SMs and dummy portions SMd. The sensor portionsSMs and the dummy portions SMd extend in the first direction Dx and arealternately arranged in the second direction Dy. The sensor portions SMsare coupled to the coupling wire 34 a or the coupling wire 34 billustrated in FIG. 5, and mainly function as detection electrodes. Thedummy portions SMd are electrically separate from the sensor portionsSMs and the coupling wires 34 a and 34 b. The dummy portions SMd aredummy electrodes not functioning as the detection electrodes.

The sensor portions SMs and the dummy portions SMd include the firstconductive thin wires 33U and the second conductive thin wires 33V andhave a similar mesh shape. This structure can prevent variations intransmittance of light in the display region AA, thereby enabling goodviewability. The sensor portions SMs are electrically separate from thedummy portions SMd by slits SL provided to the first conductive thinwires 33U and the second conductive thin wires 33V. The slits SL areprovided to the respective first conductive thin wires 33U and therespective second conductive thin wires 33V constituting one meshportion of the dummy portion SMd. The slit SL or the dummy portion SMdare not necessarily provided.

As illustrated in FIG. 5, the coupling wires 34 a are each coupled to afirst wire 37 a. The coupling wires 34 b are each coupled to a secondwire 37 b. In other words, according to the present embodiment, thefirst wire 37 a is coupled to one end of the wiring unit for temperaturedetection SM and the second wire 37 b is coupled to the other end of thewiring unit for temperature detection SM. The first wire 37 a is routedalong the peripheral region FR. The second wire 37 b is routed along theperipheral region FR.

The first wire 37 a and the second wire 37 b coupled to one wiring unitfor temperature detection SM are coupled to different terminals 36.Specifically, the first wire 37 a as the one end of the wiring unit fortemperature detection SM and the second wire 37 b as the other endthereof are pulled out to the flexible substrate 72 through therespective terminals 36. The first wire 37 a and the second wire 37 b ofthe wiring unit for temperature detection SM are electrically coupled tothe resistance detection circuit 120 illustrated in FIG. 2 through theflexible substrate 72. The resistance detection circuit 120 detects achange in resistance in accordance with a change in temperature, betweenthe first wire 37 a as the one end of the temperature detection unit SMand the second wire 37 b as the other end of the wiring unit fortemperature detection SM.

The first wire 37 a and the second wire 37 b can be made of the samemetal material or alloy as that used for the first conductive thin wires33U and the second conductive thin wires 33V. The first wire 37 a andthe second wire 37 b may be made of any material having goodconductivity, and may be made of a material different from that of thefirst conductive thin wires 33U or the second conductive thin wires 33V.

The wiring unit for temperature detection SM is not limited to theconfiguration of mesh-like metal thin wires, and may have aconfiguration including zig-zag metal thin wires or wavy metal thinwires, for example. While FIG. 6 illustrates the sensor portions SMs andthe dummy portions SMd included in one wiring unit for temperaturedetection SM, the dummy electrode may be interposed in a space SPbetween adjacent wiring units for temperature detection SM.

As illustrated in FIG. 4, the shield conductive layer 51 illustrated inFIG. 4 is provided to prevent electrostatic buildup when the displaydevice 2 is manufactured or used. Without the shield conductive layer51, electromagnetic noise such as static electricity from the outsidemay possibly hinder full effectiveness of suppressing electromagneticnoise due to a region without the first conductive thin wires 33U or thesecond conductive thin wires 33V. Further, the dummy portions SMd are inan electrically floating state, in which the dummy portions SMd are notcoupled to the sensor portions SMs, the first wire 37 a, or the secondwire 37 b. Consequently, electrification charge is hard to be removedfrom the dummy portions SMd. For this reason, static buildup in thepolarizing plate 35 or in the dummy portions SMd may possibly change theorientation of the liquid crystal layer 8, which may lead to lowerdisplay quality.

In the first embodiment, as illustrated in FIG. 4, the shield conductivelayer 51 is provided on the second substrate 31, and the sensor portionsSMs and the dummy portions SMd of the wiring unit for temperaturedetection SM are provided on the shield conductive layer 51. In otherwords, the shield conductive layer 51 is interposed between the secondsubstrate 31 and the first conductive thin wires 33U and the secondconductive thin wires 33V in the direction perpendicular to the secondsubstrate 31. As illustrated in FIG. 5, the wiring units for temperaturedetection SM are disposed at positions overlapping with the shieldconductive layer 51 in a plan view.

The shield conductive layer 51 is in direct contact with and overlapswith the first conductive thin wires 33U and the second conductive thinwires 33V of the sensor portions SMs and the dummy portions SMd. Asillustrated in FIG. 5, the shield conductive layer 51 is formed onsubstantially the entire surface of the second substrate 31, andprovided on the entire surface of the display region AA and extending tothe peripheral region FR. That is, the shield conductive layer 51 has aportion overlapping with the first conductive thin wires 33U and thesecond conductive thin wires 33V and a portion not overlapping with thefirst conductive thin wires 33U or the second conductive thin wires 33V.

The shield conductive layer 51 preferably extends to the edges of thesecond substrate 31. The shield conductive layer 51 is electricallycoupled to a fixed potential such as a power source or the groundthrough a conductive tape or the like in the peripheral region FR.

The shield conductive layer 51 is preferably provided at a positionoverlapping with the coupling wires 34 a and 34 b and the first wires 37a and the second wires 37 b as illustrated in FIG. 5. The area of theshield conductive layer 51 in a plan view is larger than a total of theareas of the first conductive thin wires 33U and the second conductivethin wires 33V.

A sheet resistance value of the shield conductive layer 51 is, forexample, from 10⁵ Ω/sq to 10¹¹ Ω/sq inclusive. More preferably, thesheet resistance value of the shield conductive layer 51 is, forexample, from 10⁹ Ω/sq to 10¹¹ Ω/sq inclusive. The sheet resistancevalue of the shield conductive layer 51 is higher than that of the firstconductive thin wires 33U and the second conductive thin wires 33V.Consequently, even if the shield conductive layer 51 is coupled to afixed potential, a change in resistance of the wiring units fortemperature detection SM in accordance with a change in temperature canbe detected.

The sheet resistance value of 10⁵ Ω/sq or higher requires the shieldconductive layer 51 to have a film thickness of 5 nm or smaller.Alternatively, one or more dispersants selected from SiO₂, TiO₂, Ta₂O₅,Nb₂O₅, and MgF₂ may be dispersed in the base material of the shieldconductive layer 51, thereby making the sheet resistance value of theshield conductive layer 51, for example, 10⁵ Ω/sq or higher. Thetransmittance of the base material of ITO, even if SiO₂ is dispersedtherein, is hard to be reduced, so that the shield conductive layer 51is preferably made of ITO, in the base material of which SiO₂ isdispersed.

As described above, the shield conductive layer includes: one or morebase materials selected from ITO, IZO, and SnO; and one or moredispersants selected from SiO₂, TiO₂, Ta₂O₅, Nb₂O₅, and MgF₂. Thiscomposition allows the shield conductive layer 51 to have the sheetresistance value of 10⁵ Ω/sq or higher, which can prevent a shortcircuit between adjacent wiring units for temperature detection SM (seeFIG. 5) or between the sensor portion SMs and the dummy portion SMd.

The sheet resistance value is a resistance value between opposing twosides of a resistor having a square shape in a plan view. The sheetresistance value of the shield conductive layer 51 can be measured by apublicly known four-terminal method, for example, using a conductivelayer deposited on the second substrate 31 by a sputtering method or thelike.

As described above, the display device 2 according to the firstembodiment includes: the second substrate 31; the wiring units fortemperature detection SM provided on a plane parallel to the secondsubstrate 31 and each including a plurality of first conductive thinwires 33U and a plurality of second conductive thin wires 33V (metalwires); and the shield conductive layer 51 in contact with andoverlapping with the first conductive thin wires 33U and the secondconductive thin wires 33V and interposed between the second substrate 31and the first conductive thin wires 33U and the second conductive thinwires 33V in the direction perpendicular to the second substrate 31. Theshield conductive layer 51 has a higher sheet resistance value than thatof the first conductive thin wires 33U and the second conductive thinwires 33V.

Manufacturing Method

FIG. 7 is a process chart for explaining a manufacturing method of thewiring units for temperature detection according to the firstembodiment. First, as illustrated in FIG. 7, the shield conductive layer51 is formed using the material including ITO and SiO₂ on the uppersurface of the second substrate 31, and a conductive layer 331 is formedusing the metal material described above on the shield conductive layer51. Subsequently, a conductive layer 332 is formed using the metalmaterial described above on the conductive layer 331 (Step ST1). Thefilm formation of the shield conductive layer 51, the conductive layer331, and the conductive layer 332 can be sequentially performed in oneprocess by the sputtering method or the like.

The conductive layer 331 may be a multilayered body in which at leasttwo of the following layers are stacked: a metal layer including one ormore elements selected from aluminum (Al), copper (Cu), silver (Ag),molybdenum (Mo), chromium (Cr), titanium (Ti), and tungsten (W); and ametal alloy layer including these elements. In the same manner, theconductive layer 332 may be a multilayered body in which at least two ofthe following layers are stacked: a metal layer including one or moreelements selected from aluminum (Al), copper (Cu), silver (Ag),molybdenum (Mo), chromium (Cr), titanium (Ti), and tungsten (W); a metalalloy layer including these elements; an oxide layer composed mostly oftin oxide (SnO₂) and silicon dioxide (SiO₂); and an oxide layer composedmostly of gallium oxide (Ga₂O₃), indium oxide (In₂O₃), and tin oxide(SnO₂).

The material of the conductive layer 332 is selected from those having alower reflectance than that of the conductive layer 331. With thismaterial, the conductive layer 332 has a lower reflectance of visiblelight than that of the conductive layer 331 and has a color closer toblack than that of the conductive layer 331 is to black.

Making the color of the conductive layer 332 closer to black than thatof the conductive layer 331 increases a resistance value of theconductive layer 332. Thus, the material of the conductive layer 331 isselected from those having higher conductivity than that of theconductive layer 332. This configuration can prevent increase in powerconsumption in the wiring units for temperature detection SM.

Subsequently, resists 335 are formed on the conductive layer 332 (StepST2). The resists 335 are patterned by photolithography to have patternscorresponding to the positions of the first conductive thin wires 33Uand the second conductive thin wires 33V as illustrated in FIG. 5.

Part of the conductive layers 331 and 332 exposed from the resists 335is etched and removed (Step ST3). The part of the conductive layers 331and 332 overlapping with the resists 335 is hard to be removed byetching, and is formed as patterns of the first conductive thin wires33U and the second conductive thin wires 33V.

Etchant for the conductive layer 331 and the conductive layer 332 needsto be changed as appropriate depending on the material. In the case of ametal film including aluminum, phosphate etchant such as phosphoric acidand acetic acid may be used. In the first embodiment, an etching rate(reduction amount of the film in contact with the etchant per unit time)of the shield conductive layer 51 is lower than that of the conductivelayer 331. After the part of the conductive layer 331 and the conductivelayer 332 not overlapping with the resists 335 is removed, the shieldconductive layer 51 functions as an etching stopper, and stops furtheretching. In this case, the shield conductive layer 51 is slightly etchedat portions 51 b not overlapping with the resists 335, thereby formingtapered surfaces 51 a.

The etching rate (reduction amount of the film in contact with theetchant per unit time) of the conductive layer 332 is lower than that ofthe conductive layer 331. Accordingly, the conductive layer 332 has alarger width than that of the conductive layer 331. Consequently, awidth of the first conductive thin wire 33U or the second conductivethin wire 33V corresponds to a width of the conductive layer 332.

After the removal of the resists 335, the conductive thin wires 33 arepatterned to be the first conductive thin wires 33U or the secondconductive thin wires 33V on the shield conductive layer 51 (Step ST4).While FIG. 7 illustrates two wires of the first conductive thin wires33U and the second conductive thin wires 33V, the process describedabove is simultaneously performed on the entire surface of the secondsubstrate 31. This process forms the wiring units for temperaturedetection SM including the first conductive thin wires 33U and thesecond conductive thin wires 33V as illustrated in FIG. 5. The firstconductive thin wires 33U and the second conductive thin wires 33V ofthe wiring units for temperature detection SM are directly stacked onthe shield conductive layer 51.

Measurement of Temperature

FIG. 8 is a graph illustrating a resistance change rate of one wiringunit for temperature detection with respect to temperature. FIG. 9 is agraph for explaining an exemplary distribution of resistance changerates of the wiring units for temperature detection. As illustrated inFIG. 8, the resistance change rate of the wiring unit for temperaturedetection SM with respect to a resistance value at a referencetemperature changes linearly in accordance with a temperature, forexample.

As illustrated in FIG. 1, the HUD device 1 may introduce sunlight LLthrough an opening 4S of the housing 4 depending on the relativeposition of the sun SUN. The sunlight LL is guided by the optical systemRM and collected as it approaches the display device 2, and may strikepart of the display region. Since the collected sunlight can deterioratethe display device, the detection of a partially heated state of thedisplay region has been demanded.

In the first embodiment, as illustrated in FIG. 5, the wiring units fortemperature detection SM are arrayed at positions overlapping with thedisplay region AA in a plan view. With this configuration, if there is awiring unit for temperature detection SM that has undergone atemperature rise, a position in the display region AA where the sunlightLL strikes can be grasped.

Assume that the wiring units for temperature detection SM includingwiring units for temperature detection SM1 to SMk illustrated in FIG. 9are arrayed in the direction Dy in the display region AA illustrated inFIG. 5. The resistance detection circuit 120 converts resistance valuesof the wiring units for temperature detection SM1 to SMk from analog todigital and outputs the detected resistance signals to the controlcircuit 110. As illustrated in FIG. 9, when the resistance change rateof the wiring unit for temperature detection SM9 is higher than that ofthe wiring units for temperature detection SM1 to SM7 and SM11 to SMk bya certain threshold or more, the control circuit 110 can determine thatthe region where the sunlight LL strikes is a region overlapping withthe wiring unit for temperature detection SM9 in the display region AA.

Meanwhile, when the sunlight LL strikes the wiring unit for temperaturedetection SM, the sunlight LL may be reflected at the wiring unit fortemperature detection SM. As illustrated in FIG. 1, even if the mountingpositon of the display device 2 is adjusted so that the regularreflection of the sunlight LL does not return to the windshield WS,light diffracted at the first conductive thin wires 33U and the secondconductive thin wires 33V may possibly reach the windshield WS.

In the first embodiment, the wiring units for temperature detection SMof the display device 2 are disposed at positions overlapping with thesecond substrate 31 having the display region, and more specifically,disposed at positions overlapping with the display region AA in a planview. The wiring units for temperature detection SM include the firstconductive layer 331 stacked above the second substrate 31 and thesecond conductive layer 332 stacked on the first conductive layer 331.The second conductive layer 332 has a lower reflectance of visible lightthan that of the first conductive layer 331. This configuration preventsdiffraction of light at the wiring units for temperature detection SMeven when the sunlight LL strikes the wiring units for temperaturedetection SM. This improves the display quality of the image VIrecognized within the field of view of the user H illustrated in FIG. 1.

Since the width of the second conductive layer 332 is larger than thewidth of the first conductive layer 331 as illustrated in FIG. 7, lightreflected at the first conductive layer 331 is covered by the secondconductive layer 332, thereby preventing the diffraction of light at thewiring units for temperature detection SM.

First Modification of First Embodiment

The material of the shield conductive layer 51 is not limited to ITO.The material of the shield conductive layer 51 is, for example, aconductive material having a carbon nanotube structure and having avisible light transmittance of 90% or higher. The sheet resistance ofthe shield conductive layer 51 is, for example, from 10⁵ Ω/sq to 10¹¹Ω/sq inclusive. The conductive material with the carbon nanotubestructure is less susceptible to light-induced resistance change thanITO. If heat and light simultaneously act on the shield conductive layer51 and the wiring units for temperature detection SM, the resistancechange in accordance with temperature change due to light is prevented,and the detection accuracy of the resistance change in accordance with atemperature changed by heat is increased.

Second Modification of First Embodiment

The material of the shield conductive layer 51 is, for example, aconductive polymeric material such as poly-3,4-ethylenedioxythiophene(PEDOT). The sheet resistance of the shield conductive layer 51 is, forexample, form 10⁵ Ω/sq to 10¹¹ Ω/sq inclusive. The conductive polymericmaterial is less susceptible to light-induced resistance change thanITO. If heat and light simultaneously act on the shield conductive layer51 and the wiring units for temperature detection SM, the resistancechange in accordance with temperature change due to light is prevented,and the detection accuracy of the resistance change in accordance with atemperature changed by heat is increased.

Third Modification of First Embodiment

The material of the shield conductive layer 51 is, for example,antimony-doped tin oxide (ATO). The sheet resistance of the shieldconductive layer 51 is, for example, from 10⁵ Ω/sq to 10¹¹ Ω/sqinclusive. The ATO conductive material is less susceptible tolight-induced resistance change. If heat and light simultaneously act onthe shield conductive layer 51 and the wiring units for temperaturedetection SM, the resistance change in accordance with temperaturechange due to light is prevented, and the detection accuracy of theresistance change in accordance with a temperature changed by heat isincreased.

Second Embodiment

FIG. 10 is a sectional view of a wiring unit for temperature detectionaccording to a second embodiment. The same constituent elementsdescribed in the first embodiment are denoted by the same referencesigns, and overlapping explanation thereof is omitted.

In the second embodiment, an insulating layer 52 is formed on the shieldconductive layer 51. The conductive layer 331 is formed on theinsulating layer 52. The conductive layer 332 is formed on theconductive layer 331. With this configuration, the insulating layer 52insulates the shield conductive layer 51 from the conductive thin wires33 serving as the first conductive thin wires 33U or the secondconductive thin wires 33V. In other words, the insulating layer 52insulates the shield conductive layer 51 from the wiring units fortemperature detection SM. As a result, simultaneous acting of heat andlight on the shield conductive layer 51 and the wiring units fortemperature detection SM may cause the resistance change in accordancewith temperature change due to light, but have no effect on theresistance change in accordance with a temperature changed by heat inthe wiring units for temperature detection SM.

Third Embodiment

FIG. 11 is a sectional view for explaining a wiring unit for temperaturedetection according to a third embodiment. The same constituent elementsdescribed in the first embodiment are denoted by the same referencesigns, and overlapping explanation thereof is omitted.

In the third embodiment, the conductive layer 331 is formed on thesecond substrate. The conductive layer 332 is formed on the conductivelayer 331. The protection layer 38 is formed on the conductive layers331 and 332. The protection layer 38 is made of a translucent resin,such as an acrylic resin having insulation properties. The shieldconductive layer 51 is formed on the protection layer 38. In otherwords, the wiring units for temperature detection SM and the shieldconductive layer 51 are disposed above the second substrate 31, and thewiring units for temperature detection SM are stacked below the shieldconductive layer 51. This configuration prevents the shield conductivelayer 51 from being etched during the formation of the conductive layers331 and 332 as described in the first embodiment, and thus increases thequality of the shield conductive layer 51 and increases the accuracy ofthickness. The protection layer 38 insulates the shield conductive layer51 from the wiring units for temperature detection SM. As a result,simultaneous acting of heat and light on the shield conductive layer 51and the wiring units for temperature detection SM may cause theresistance change in accordance with temperature change due to light,but have no effect on the resistance change in accordance with atemperature changed by heat in the wiring units for temperaturedetection SM.

The present invention can naturally provide other advantageous effectsthat are provided by the aspects described in the embodiments above andare clearly defined by the description in the present specification orappropriately conceivable by those skilled in the art.

While exemplary embodiments according to the present disclosure havebeen described, the embodiments are not intended to limit the presentdisclosure. The contents disclosed in the embodiments are given by wayof example only, and various changes may be made without departing fromthe spirit of the present disclosure. Appropriate changes made withoutdeparting from the spirit of the present disclosure naturally fallwithin the technical scope of the present disclosure.

While a liquid crystal panel exemplifies the display device 2 in theabove description, the display device 2 may be an organicelectroluminescence (EL) panel or a micro light-emitting diode (LED)display that displays an image by emitting different light rays fromdifferent LEDs. The LEDs each have a size from 3 μm to 100 μm inclusivein a plan view.

What is claimed is:
 1. A head-up display device comprising: a backlight;a display device provided above the back light; and an optical systemprovide above the display device, wherein the display device including:a substrate; a shield conductive layer; a plurality of wiring units thatare for temperature detection; and an insulating layer, the shieldconductive layer is provided above a surface of the substrate on anoptical system side, and the wiring units are stacked on the shieldconductive layer with the insulating layer interposed therebetween, sothat the wiring units and the shield conductive layer are insulated fromeach other.
 2. The head-up display device according to claim 1, whereinthe display device has a display region, and the wiring units aredisposed at a position overlapping the display region when seen in aplan view.
 3. The head-up display device according to claim 1, eachwiring unit has one end coupled to a first wire and the other endcoupled to a second wire, to detect resistance that changes inaccordance with a change in temperature, between the first wire and thesecond wire.
 4. The head-up display device according to claim 1, whereinthe shield conductive layer has a higher sheet resistance value thanthat of the wiring units.
 5. The head-up display device according toclaim 1, wherein the shield conductive layer includes one or more basematerials selected from the group consisting of ITO, IZO, and SnO andincludes one or more dispersants selected from the group consisting ofSiO₂, TiO₂, Ta₂O₅, Nb₂O₅, and MgF₂.
 6. The head-up display deviceaccording to claim 1, wherein the shield conductive layer is made of oneor more materials selected from the group consisting of a conductivematerial with a carbon nanotube structure, PEDOT, and antimony-doped tinoxide.